Abstract

The difference in center frequency between the two counterpropagating pulses in a mode-locked dye ring laser can be varied from 0 to 1 MHz by modulating an intracavity Pockels cell synchronously with the cavity frequency (Fig. 1). The two trains of counterpropagating pulses are interfered at a photodiode, where the difference in frequency is measured as a beat note. Differences in center frequency of 100 Hz can be resolved, even with pulses of 10-THz bandwidth. This control of relative-frequency splitting can be used to carry out accurate spectroscopic measurements.

© 1994 Optical Society of America